Truck Loading

[BadgerPE]

I have a contractor that wants to drive construction equipment and supply trucks (i.e. concrete trucks, dump trucks, etc.) over an existing precast tunnel. The 20' planks were specified to be designed in accordance with HS-20 requirements. I can't find any information if the HS-20 loading is appropriate for this situation. I know it is a popular bridge designation, so I think it would be. However, a few google searches have shown that some of the trucks may exceed the 32k rear axle load requirement. How is this typically handled on a bridge project? It seems that any bridge would be required to be designed for HS-20 would also be subject to heavy concrete/dump truck loads as well.

 

[JedClampett]

You're going to have to tote that barge and lift that bale. There's no safe way to assume a load larger than the HS20 load is always going to work for some element designed for HS20. Sometimes you can eliminate the impact load for slow speeds, or distribute the loads over a larger footprint due to the structure's depth, but the only safe way is to find the actual design and check it for the larger load.

 

[Lomarandil]

Yes -- every state handles overload situations differently, but for loads in excess of the state legal load (usually a combination of an HS-20/HL-93 load and a few differing military/permit vehicles), you need to perform the overload analysis.

Do you know that your tunnel is only designed for HS-20 and not one of those other design vehicles as well?

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The name is a long story -- just call me Lo.

 

[JoelTXCive]

I have had to deal with this recently on an older bridge. I agree with Jed & Lo that you have to do the analysis.

Unfortunately, the 'HS-20' designation does not give you enough info.

I'm guessing your bridge was 'pre-1993'

The HL-93 design model designation would tell you that the bridge was designed for the HS-20 truck plus the design lane. It would also tell you that the bridge could handle the design tandem (~concrete truck) plus the design lane.

 

[Lomarandil]

Or tell your contractor to work with legal load vehicles. They're out there, even for heavy construction activities (might have to rent them from a bridge contractor).

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The name is a long story -- just call me Lo.